1. Field of the Invention
This invention relates to a new material for forming a metal image, specifically, to a metal image-forming material which has the ability to form an image of high contrast, and is suitable for linework and halftone dot images.
2. Description of the Prior Art
An image-forming material called a chrome mask, which consists of a glass sheet, a chromium layer formed thereon by vacuum deposition, and a photosensitive resin layer on top of the chromium, is known. With this image-forming material, the cured resin layer after exposure and development becomes an etching resist, and by etching removal of the chromium layer a master print board for integrated circuits is produced. Since chromium is used in this image-forming material, images formed thereon are tough, but etching at the time of image formation is difficult. Furthermore, environmental pollution due to chromium ions dissolved in the etching solution poses a serious problem.
Japanese Patent Publication (OPI) Nos. 65927/73 and 65928/73 disclose an image-forming substance which is a vacuum deposited coating of a composition containing tellurium. Tellurium, however, is available only in small amounts, and is toxic.
Considering the above factors, aluminum is considered to be a desirable image-forming metal substance. The greatest defect of aluminum is that aluminum is difficult to etch with an etching solution of a simple composition. Because of this, long periods of time are usually required for etching, and, therefore, a material having strong resistance to etching must be used as an etching resist. In addition, it is difficult to obtain sharp, clear images, and their edges blur.
In an attempt to solve these problems with conventional techniques, we have investigated the etchability of aluminum (which is a non-toxic image-forming substance) in an image-forming material. These investigations led to the present invention.